1. Field of the Invention
Implementations of various technologies described herein generally relate to seismic data processing, and more particularly, seismic data processing of irregularly sampled seismic data.
2. Description of the Related Art
The following descriptions and examples do not constitute an admission as prior art by virtue of their inclusion within this section.
In a typical seismic survey, a plurality of seismic sources, such as explosives, vibrators, airguns or the like, may be sequentially activated at or near the surface of the earth to generate energy which may propagate into and through the earth. The seismic waves may be reflected back by geological formations within the earth. The resultant seismic wave field may be sampled by a plurality of seismic sensors, such as geophones, hydrophones and the like. Each sensor may be configured to acquire seismic data at the sensor's location, normally in the form of a seismogram representing the value of some characteristic of the seismic wave field against time. The acquired seismograms or seismic data may be transmitted wirelessly or over electrical or optical cables to a recorder system. The recorder system may then store, analyze, and/or transmit the seismograms. This seismic data may be used to detect the possible presence of hydrocarbons, changes in the subsurface and the like.
In some circumstances, the sampled seismic data may be acquired at irregular locations. That is, the seismic data may be acquired from locations which were not planned to be sampled. For example, seismic data may be planned to be sampled in a first location. However, an obstacle (e.g., a building) may be located on top of the first location. Consequently, a sensor or receiver may not be placed at the planned first location. Therefore, the sensor may have to be placed in a second location that is close to the first location, but is not the same as the planned location. This second location may be referred to as an irregular location. Many receivers may acquire seismic data at irregular locations, thereby resulting in irregularly spaced seismic data.
After acquiring sampled seismic data, the seismic data may be processed using specific signal-processing algorithms. For example, Fourier transforms may be applied to the seismic data. The signal-processing algorithms may require the seismic data to be located at regularly spaced locations. For example, the algorithms may require the seismic data to be located at the nodes of a regularly spaced grid (e.g., a Cartesian grid). If the seismic data is not located at regularly spaced locations, the results of the signal-processing algorithms may be inaccurate or distorted. Consequently, using irregularly sampled seismic data may result in inaccurate or distorted results.
One solution to the problem of having seismic data at irregularly spaced locations while the seismic data is needed at regularly spaced locations is to use the seismic data at the irregularly spaced locations to estimate the seismic data at regularly spaced locations. Obtaining seismic data at regular locations from seismic data which was measured at irregular locations is commonly referred to as re-sampling or interpolation. The process of interpolating or re-sampling seismic data onto a regular grid from seismic data sampled at irregular locations is called regularization or gridding. Regularization of seismic data is often a very important pre-processing step for several seismic data processing algorithms, including 3-dimensional surface-related multiple attenuation (SRME), migration and 4-dimensional survey matching. Although the aforementioned interpolation techniques allowed for estimation of seismic data from irregularly spaced samples, the interpolated seismic data still suffers from the effects of noise.